ENHANCEMENT OF SEISMIC BEHAVIOR OF STEEL MOMENT FRAME WITH CHANGE OF BRACING SYSTEM CONFIGURATION ON HEIGHT

  S.A.R. Kaboli1, M. Gerami2,*, A. Mirhaj3     1. Lecturer, Department, Islamic Azad University, Firouzkooh, Iran   2. Assistant Professor , Civil Engineering Faculty, Semnan University, Semnan, Iran   3. MSc. Student , Civil Engineering Faculty, Semnan University, Semnan, Iran   * Corresponding Author : mgerami@semnan.ac.ir     Abstract   One of the custom seismic structural systems for mid-rise and high-rise steel structures is braced steel moment frames. Each bracing systems behaves differently at earthquake. To reach useful applications of these bracing systems, seismic behavior at steel structures braced with eccentric (EBF) or concentric (CBF) bracing systems is rarely investigated. Having correct understanding of bracing behaviors and design at such structures are very important in order to assure appropriate dual performance. Hence most accuracy must be made in selecting of bracing system types and its configuration to satisfy code requirements and serviceability. Because of material nonlinearity that will be necessarily accurse in the structure due to real earthquake in the absence of nonlinear dynamic analysis, static nonlinear pushover method can approximately describes the inelastic behavior of structure. 10, 15, 20 and 30 story 2D steel moment frames braced with CBF and EBF have been modeled in this study. Effects of change of bracing systems level from CBF to EBF with respect to nonlinear behavior of structure based on the area of load-displacement diagram are investigated. Analytical results obtained from over 100 analysis show that change of bracing system configuration at the specific level of structure changes the pattern of plastic hinges formation and cause to increase the general ductility.